1. Field of the Invention
This invention relates generally to the practice of prosthodontia and more particularly to a processor implemented system for design and fabrication of dental restorations.
2. Antecedents of the Invention
Prior methods of fabrication of dental restoratives, prosthesis or restorations such as crowns, bridges and the like, were taxing, time consuming procedures entailing both a dental practitioner as well as a laboratory technician. The dental practitioner generally utilized a dental impression material to form impressions, with the impressions then being employed to cast rigid models, which were then utilized by the dental laboratory technician to fabricate the restoration.
The precise dimensions, shape and coloration of the restoration were subjective parameters, dependent upon the expertise and experience of both the dental practitioner and the dental laboratory technician. Emplacement of the restoration in the oral cavity was also a time consuming practice which involved grinding surfaces of the restoration for occlusal and interproximal fit. Often, a restoration which fit well would be unsatisfactory in hue, chroma, luminous intensity or opacity, due to the subjective nature of color matching and the effects of artificial light at the practitioner's office which resulted in imperfect color matching when the restoration was viewed under different lighting conditions.
The procedure was expensive, labor intensive, time consuming and an inconvenience to the patient, due to the requirement for numerous visits to the dental practitioner.
With the advent of computer aided design systems, attempts were made to utilize processors for determining the shape of a restoration, based upon physical measurements or optical scans of the restoration site in combination with the utilization of processor controlled fabrication, e.g. cutting or milling of the restoration itself. Examples of typical proposed CAD-CAM systems were disclosed in the patents to CARLSSON, U.S. Pat. No. 5,851,115, NONOMURA, U.S. Pat. No. 5,555,884, JOHANNSON, U.S. Pat. No. 5,320,462, VAN ZER ZEL, U.S. Pat. No. 4,937,928, O'HARRA, U.S. Pat. No. 4,935,635 and MOERMANN, U.S. Pat. No. 4,575,805.
Further attempts were made in connection with computer-aided design of dental restorations which employed scanning a model of the restoration site and adjacent areas, as disclosed in the patents to GUIOT, U.S. Pat. No. 6,287,121, HULTGREN, U.S. Pat. No. 6,217,334 and SCHMITT, U.S. Pat. No. 5,823,778.
None of these prior systems resulted in a dental restoration having computer generated colorimetric values. Since these systems generally fabricated the restoration by milling or cutting from a block of material, the final colorimetric appearance of the restoration involved the manual application of a pigmented coating or the preselection of a starting mass or block of restoration material which was uniformly colored and selected, utilizing subjective color chart matching.